If you loved the simplicity of the IPv6 manual tunnel we created in Part 1, you should love the Generic Routing Encapsulation (GRE) approach to tunneling IPv6 traffic through an IPv4 cloud just as much.

This simple approach takes the IPv6 packet and encapsulates it using the standard IPv4 GRE tunnel. But wait a minute? In Part 1 of this blog series, we had IPv4 encapsulate the IPv6 packet directly for tunneling across the v4 cloud. Why do we even need this additional method that adds GRE encapsulation to the process? Well, the answer is that this method is required within integrated IS-IS and IPv6 tunnel environments. If you plan on sending both IS-IS traffic and IPv6 traffic over the tunnel, you need the protocol field of the GRE header that allows identification of the passenger protocol.

This blog series was recommended by another of our awesome students and IEOC community members, Marcio A. Costa.

In the first part of this series, we will look at the Manual IPv6 tunnels that are simple to create in order to connect two “islands” of IPv6 separated by IPv4-only devices. For this blog, we will use the following simple topology: